Something very strange

My friend has a 6S and yesterday she decided to update to iOS 13.2.2 from iOS 12.4.1. Keep in mind, she doesn't have Wifi at home so she can't updateher software as easily as most of us can so she has to wait until she's somewhere there is Wifi. So yesterday she was near Wifi and plugged her device in and went to sleep. She told me later that her phone updated only to iOS 12.4.2 instead of iOS 13.2.2. I thought that maybe she had an iPhone older than the 6S and told her that it won't update any further. However, today, her phone gave her a message that iOS 13.2.2 was available for download. This is very strange, I've never heard of this. When she went to check if her software was up to date yesterday after it installed to iOS 12.4.2, it said it was.